In many hydraulically actuated devices, such as hydraulically actuated fuel injectors, a three way valve assembly controls the operation of the device. In general, the valve assembly opens an internal work flow passage to a high pressure passage when the device is operating, such as to hydraulically move a piston. Between operation events, the work flow passage is opened to a low pressure passage or drain so that the used fluid in the flow passage can be removed, and the device reset for its next operation event. In the case of a hydraulically actuated fuel injector, high pressure fluid acts on a pumping element to pressurize fuel during an injection event, and the pumping element retracts and resets between injection events. In some cases, the control valve assembly consists essentially of a poppet valve member that is moved between a pair of conical valve seats by a solenoid actuator.
Although the relatively simple solenoid actuated poppet valves have performed well for many years, engineers are always seeking ways to improve performance, increase reliability and reduce costs. In addition, there is often a trend to add additional functions to the control valve assembly to perform additional functions, such as controlling a direct control needle valve in a fuel injector. One response to these trends is to substitute a pilot actuated valve that utilizes a relatively small solenoid to move a small pilot member, which in turn controls the positioning of a relatively larger spool valve that opens and closes the high and low pressure passages. These pilot actuated valves can come in a variety of designs, including those in which the pilot member is a ball, or is a relatively small poppet valve member that moves between conical valve seats. While these newer pilot valve assemblies have performed well, there still remains room for improvement in areas such as reducing part count, improving concentric alignment between valve components, integrating the valve assembly in a relatively small package, and improving the ability of the valve assembly to simultaneously control two or more functions, such as fuel pressurization and injection timing.
The present invention is directed to improving upon these and other aspects of pilot actuated valve assemblies, especially as they relate to fuel injectors.